1. Field of the Invention
This invention relates to an electronic circuit element, and more particularly to an electronic circuit element which is adapted to be fixedly mounted on a printed circuit board by soldering while being stably provisionally fixed on the board by means of an adhesive.
2. Description of the Prior Art
Conventionally, mounting of a plurality of electronic circuit elements on a single printed circuit board is typically carried out in such a manner that a predetermined number of electronic circuit elements are provisionally held at predetermined positions on the printed circuit board and then practically secured to the printed circuit by soldering.
Such an electronic circuit element is generally classified into two types or a surface-mounted-type electronic circuit element which is adapted to be fixed on a conductive pattern formed on a printed circuit board and a lead-type electronic circuit element which is adapted to be vertically mounted with respect to a printed circuit board by securely inserting lead wires of the element via through-holes of the printed circuit board and soldering the lead wires to the board.
The surface-mounted-type electronic circuit element includes a chip-type electronic circuit element such as a chip capacitor or the like and a special-type electronic circuit element such as an IC or the like. Provisional or temporary fixing of the surface-mounted-type electronic circuit element on a printed circuit board which is carried out prior to soldering operation is generally performed by previously applying an adhesive to a circuit element mounting portion of the printed circuit board by screen printing or the like and then placing the circuit element on the printed circuit board by means of a suction of head of an automatic mounting apparatus to provisionally fix the element on the printed circuit board through the adhesive. Previous application of the adhesive to the printed circuit board renders direct stacking of the printed circuit boards impossible, resulting in handling of the printed circuit boards being highly troublesome. In view of such a problem, it is proposed that the provisional fixing is carried out by previously preparing an electronic circuit element series which comprises a carrier tape and a plurality of electronic circuit elements held on the carrier tape through a thermosetting adhesive applied onto a flat surface of the carrier type, then extracting the circuit elements one by one from the carrier tape means of a suction head of an automatic mounting apparatus and placing the circuit elements on a printed circuit board by the suction head to provisionally fix them on the printed circuit board through the thermosetting adhesives which may adhere to the sides of the electronic circuit elements when the electronic circuit elements are removed from the tape. An example of an electronic circuit element series of this kind is found, for example, in Japanese Utility Model Registration No. 1405587 (Japanese Utility Model Publication No. 11438/1981) to TDK Corporation.
Unfortunately, the proposed techniques fail to facilitate operation of releasing or extracting the electronic circuit elements from the carrier tape by the section head because the adhesive firmly holds the circuit elements on the carrier tape to a degree sufficient to prevent the smooth peeling-off. Even when the electronic circuit element is released from the tape, it pulls the carrier tape through the adhesive during the peeling-off operation. This results in the carrier tape acting on electronic circuit elements adjacent to the released one when it elastically returns to the original position, to thereby cause them to be separated from the carrier tape. Another disadvantage of the prior art is that the adhesive remains on the carrier tape to fail in sticking to the circuit element when the element is peeled off from the carrier tape.
Mounting of a lead-type electronic circuit element on a printed circuit board is generally carried out by clinching operation wherein lead wires of the circuit element inserted via through-holes of the printed circuit board are each perpendicularly bent at a tip end thereof projected outwardly from the board, so that the circuit element may be provisionally fixed on the printed circuit board by cooperation between the bent lead wires and a kink formed along an axis of each of the lead wires by bending. Then, the previously fixed lead-type electronic circuit element is practically secured to the printed circuit board by soldering the bent ends of the lead wires onto a rear surface of the printed circuit board.
Unfortunately, the above-described fixing procedure causes the lead-type electronic circuit element to fall down during the provisional fixing operation or transportation to a soldering station. This not only leads to a failure in the mounting but causes the perpendicularly bent tip end portions of the lead wires of the falling-down circuit element to hinder mounting of circuit elements adjacent thereto. Thus, the procedure fails in high density mounting of chip-type circuit elements on a printed circuit board.